Since June last year, the Ministry of Justice has recorded 56 cases of extreme Islamist publications being confiscated.

In the seven months from June to December 2016, 12 books were identified as "containing extremist material" likely to present a threat to good order or national security.

However, the number increased significantly between January and last month, with another 44 prisoners caught in possession of radical Islamist teachings.

The figures come after new guidelines were launched by Her Majesty's Prison and Probation Service last summer.

Ian Acheson, a former prison governor who conducted a government review last year, told The Daily Telegraph: "Radicalisation in prison is a real and present danger which we have seen growing in scale. Purveyors of hateful ideologies will take full advantage of the ungoverned spaces in British jails.

Anjem Choudary was moved to a specialist new 'jihadi jail' unit for extremistsCredit:
euters

"The prison service has an obligation to get a grip on this phenomenon and stop the hand-wringing political correctness that has prevented decisive action against extremism for so long. We simply cannot tolerate a situation where people go into prison as criminals and go out as converted terrorists."

The latest figures, which The Telegraph obtained under Freedom of Information laws, reflect the growing levels of concern at the activities of convicted Islamist hate preachers and terrorists behind bars.

Dr Usama Hasan, the head of Islamic studies at Quilliam International, the counterextremism organisation, said: "We know of several cases where 16-year-olds went into prison in the UK for petty crimes and then, two or three years later, they have been radicalised and come out as a dangerous terrorist."

The Ministry of Justice said: "We have delivered on our plans to house the most subversiveprisoners in separation centres, preventing their influence over others, and have provided more than 8,500 front-line staff with enhanced training to tackle this evolving threat."

'We cannot tolerate a situation where people go into prison as criminals and go out as terrorists'